Hydrotherapy spas are becoming increasingly popular. In addition to the pleasurable and relaxing sensation of being immersed in swirling hot water, the spas provide therapeutic benefits, such as relief from tension and sore muscles. Spas may be constructed either indoors or outdoors either by themselves or in conjunction with swimming pools.
These spas generally comprise a fiberglass shell which is on the order of 6-8 feet across and 3-4 feet deep in a round, square, hexagonal or other shape. A plurality of jet nozzles is spaced around the periphery of the shell below the water line to inject jets of aerated warm or hot water into the spa, forming swirls and eddies which provide comfort and relaxation to the bather.
Shells have heretofore conventionally been constructed by spraying liquid epoxy or other suitable resin onto the outer surface of a mold. Glass fibers are then applied to the resin and embedded therein. After the resin hardens, the shell is removed from the mold, with the inner resin or gel surface constituting the inner finished surface of the shell. Although this construction provides an inner surface initially smooth and aesthetic in appearance, the smooth resin tends over a period of time to form hairline cracks which trap dirt and detract from the appearance of the spa.
Another problem has heretofore remained unsolved in the fabrication of the spa. In the past, a hole was dug in the ground somewhat larger than the shell and its plumbing, and the shell lowered into the hole. With the shell in place, grout was pumped into the hole. Even if the shell was initially placed in the hole at the correct elevation and with no tilt, the added grout exerted an upward buoyant force on the shell which pushes the same above its desired position. Once the grout hardened, the situation could not be corrected without excessive effort. Attempts to compensate for this effect by positioning the shell lower in the hole so that the grout floated the shell upwardly to its desired position produced results which were less than satisfactory, frequently resulting in a tilted spa or a spa located above or below grade.